SOLVED : Set vertex parameter using Mogre

Hello,

I'm trying to set the parameter of a vertex shader using Mogre.

I have a parameter called "outline_thickness", and I've not found any easy way of modifying it.

I've tried

outlinePass.GetVertexProgram().GetParameter("outline_thickness").SetParameter("outline_thickness", "0.01");

and if I use outlinePass.GetVertexProgram().GetParameters() then I end up with a list that doesnt feature my parameter:

type
syntax
includes_skeletal_animation
entry_point
target

I can modify the default parameter using

Mogre.GpuProgramParametersSharedPtr tParamList=outlinePass.GetVertexProgram().GetDefaultParameters();

tParamList.SetNamedConstant("outline_thickness",10.01f);

But I cant figure out how to change the active parameter. Any help setting this parameter will be much appreciated!

Thanks,
Simon

Edit :

Sorry, just figured out I need to do this on the pass rather than the vertex program itself